Controling that json tiral files are not used more than once


I am impmenting an experiment with jsPsych (version: 6.3.0) that should be hosted on Pavlovia with participants recruited from Prolific.

The trial order is set for every participant in a json file that I load with the jquery library, i.e. $.getJSON(...). Each trial file can only be used once, so participant 1 should get file 1, participant 2 → file 2, … (or randomized, but still I need to track which files were already used).

I thought of having another json file which keeps track of the file numbers used like this:

      const used_trial_nrs = => t.trial_file_nr);
      const trials_to_delete = new Set(used_trial_nrs);
      const all_trials = [...Array(100).keys()].map(String).map(n => lpad(n,3,0));
      const available_trials = all_trials.filter((name) => {
        return !trials_to_delete.has(name);
// create random number to choose from array of available stimuli files
const random = Math.floor(Math.random() * available_trials.length);
const rand_stim_nr_from_list =  available_trials[random];    

The issue I face is how to create this file, because obviously it is not allowed to write from the index-html to the pavlovia folder.
I thought of writing a monitoring watchdog event handler that reads out the trial file used from the saved data each time a new data file is added, but that would need to be writen in javascript as well, as python scripts are not allowed to run on pavlovia.
If the data-files could be saved to a MySQL table it would be possible to read out the file-information but as I understood that is not possible, right?

I also came across @wakecarters consecutive participant ID numbers webpage ( which might be useful. If I get it right I would add this modified link than to Prolific and could then read out from the URL the assigned participant number with"participant")??

Any other ideas on how to solve this are highly appreciated!